Effect of air annealing on the structural, electrical, and optical properties of V-doped β-Ga2O3 single crystals

V impurities were intentionally introduced into beta-Ga2O3 crystals as n-type dopants to improve the n-type conductivity of single-crystal substrates. A high-quality 0.20 mol% V-doped beta-Ga2O3 single crystal was fabricated, and the effects of air annealing on the structure and the electrical and optical performances of V doped beta-Ga2O3 single crystals were systematically studied. The V-doped beta-Ga2O3 crystal exhibited a high crystal quality, smooth surface, and high carrier concentration. In comparison, the crystalline quality of beta-Ga2O3 was improved, and it showed a flat surface after the annealing treatment. Compared with that before annealing, the carrier concentration decreased from 5.90 x 10(18) to 9.51 x 10(17) cm(-3), the optical transmittance increased in the near-infrared region, and the peak intensity of the Ag(3), mid-frequency A(g)((8)), A(g)((9)) and A(g)((10)) phonons were changed, which were attributed to the electron traps of the gallium vacancy (V-Ga) and the two cation vacancies paired with one cation interstitial atom (2V(Ga)(1)-Ga-i) complex. After annealing, the oxygen vacancy (V-O) was compensated, and the Ga3+ content decreased, which were related to the decrease in the free electron concentration. The variations in the V-O and V-Ga concentrations resulted in a decrease in the blue luminescence peak area ratio and the formation of a green luminescence peak, respectively. These results can facilitate a better comprehension of the structural and property changes in V-doped beta-Ga2O3 crystals owing to air annealing. (C) 2022 Elsevier B.V. All rights reserved.

Automated summary

This study intentionally introduced V impurities to enhance the n-type conductivity of beta-Ga2O3 crystals, and systematically investigated the effects of air annealing on the structure, electrical, and optical properties of V-doped beta-Ga2O3 single crystals. The results showed improvements in the crystalline quality and surface flatness of beta-Ga2O3 after annealing, as well as changes in carrier concentration, optical transmittance, and phonon spectra. The variations were attributed to the presence of electron traps and the compensation of oxygen vacancies.